These pieces or chromosomes become shorter by slowly contracting, and thus each takes the form of an angular loop, a straight rod, or a roundish, oval, or spherical body (Fig. 74, _C_, _chrs_). While this is happening, we can see at the side of the nucleus, and closely apposed to it, a pale longitudinally striped figure with a swelling, similar to a handle, at both ends--the so-called nuclear spindle or central spindle (_ksp_). This is the apparatus for the division of the nucleus, and it was previously represented by a small body susceptible to certain stains--the centrosome, which was surrounded by a halo-like zone, the centrosphere or 'sphere.' This body was long overlooked, but now the majority of investigators assume that, though it is often inconspicuous and very difficult to make visible, it is nevertheless present in every cell which is capable of division, and that it is therefore a permanent and indispensable constituent of the cell (Fig. 74, _A_ and _B_, _csph_). When a cell is on the point of dividing, this remarkable cell-organ, which has hitherto seemed no more than an insignificant, pale, little sphere, now becomes active. First of all, often before the formation of the chromatin coil, it doubles by division (_A_ and _B_ _csph_), at first only as regards the centrosome, and then as regards the sphere also (_B_); and while division is going on fine protoplasmic filaments issue from the dividing sphere and radiate like rays from a sun into the cell-substance. As they only retain their connexion with each other at the surfaces of the dividing halves of the sphere which are turned towards each other, we might almost say that fine threads are drawn out between the two halves as they separate, and these become longer the further apart the halves diverge. In this manner the much-talked-of 'spindle figure' arises, which was first described in the seventies through the researches of A. Schneider, Auerbach, and Bütschli, but the significance and origin of which have claimed the labours of many later investigators down to our own day. The processes now to be described do not always take place in exactly the same manner, but the gist of the business is everywhere the same, and it consists in this, that the two ends or 'poles' of the spindle diverge further and further apart, and between them lies the nucleus whose membrane now disappears (_C_, _km_) while the spindle threads traverse its interior. Sometimes the membrane is retained, but nevertheless the spindle threads penetrate into the interior of the nucleus. But the chromosomes always range themselves quite regularly in the 'equatorial plane' of the spindle (_D_, _aeq_)--a process the precise mechanism of which is by no means clearly understood, and indeed the play of the forces in the whole process of nuclear division is still very imperfectly revealed to our intelligence.